Frequency changing system



July 10, 1934.

L. A. GEBHARD FREQUENCY CHANGING SYSTEM Filed Dec. 6, 1932 I5 Sheets-Sheet 1 a O O 1? '5 INVENTOR. 90M Q geedaad,

V I y M a M ATTORNEY L. A. GEBHARD 1,965,590

FREQUENCY CHANGING SYSTEM Filed Dec. 6, 1932 3 Sheets-Sheet 2 July 10, 1934.

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Patented July 10, 1934 1,905,596 FREQUENCY cnancmc srs'rau Louis A. Gebhard, Washington, D. c. Application December a, 19:2, serial No. 045.908

6 Claim (01. 111-442) (Granted under the ma March amended, April 30,1928; 370 O. G. 757) My invention relates broadly to frequency changing systems for high frequency transmitters and more particularly to a construction of frequency changing apparatus having a high degree of efliciency.

One of the objects of my invention isto provide a construction of frequency changing apparatus for high frequency signaling systems in which a high degree of efllciency of signal transmission 10 may be maintained and wherein the construction may be rendered highly compact.

Another object of my invention is to provide a construction of frequency changing apparatus for high frequency changing systems in which a single set of switch contacts are electrically connected with the oscillation circuits of the transmitter and shielded inductance coils moved into effective electrical connection with the sets of contacts while electrostatically isolating the inductance coils, which are not in use from the inductance coil which is' effective and from other parts of the signaling apparatus.

Still another object of m invention is to provide a novel form of frequency changing apparatus for high frequency signaling systems in which a multiplicity of inductance units may be mounted in electrostatically shielded compart-' ments constituted by a frame structure which is bodily movable with respect to sets of fixed contacts in permanent connection with the oscillation circuits of the transmitter with means for shifting the electrostatically shielded compartments to bring a selected inductance unit into connection with the fixed contacts while electrostatically isolating the remaining inductance units from the inductance unit which is rendered eifective.

A further object of my invention is to provide an electrostatically shielded inductance system for frequency changers wherein movement may be imparted to the entire electrostatically shielded mounting for the inductance units for rendering a selected inductance unit eifective while electrostatically isolating the remaining inductance units'from the effective inductance unit.

Other and further objects of my invention reside in the novel arrangement of parts for construction of frequency changing apparatus as set forth more fully in the specification hereinafter following by reference. to the accompanying drawings, in which:

Figure 1 is an elevational view showing the terminal connectioias for the oscillatory circuits leading to the adjustable inductance system of my invention; Fig. 2 is a side elevational view.

of the apparatus illustrated in Fig. 1, partially broken away and shown in section on line 2-2 of Fig. 1; Fig.3 is a longitudinal sectional view taken through the frequency changing apparatus on line 33 of Fig. 2; Fig. 4 is a vertical sectional view taken on line 4-4 of Fig. 3; Fig. 5 is a vertical sectional view taken through the frequency changing apparatus and illustrating the electrostatically shielded inductance shifted to another selectedposition from that illustrated in Figs. 1-4; Fig. 6 is a transverse sectional view through the frequency changing anparatus on line 6-6 of Fig. 4: Fig. '7 is a plan view of the end of one of the shield plates illussystem unit which is selected for operation in the transmitter circuits; and Fig. 10 illustrates one of the spring actuated means which I provide for maintaining the shielded compartments in a predetermined position when a particular inductance unit is selected for operation in the transmitter circuit.

In a radio frequency transmitter in which a number of coil systems are employed to cover a large band of frequencies certain objectionable features have been encountered. In order to use the transmitter at high frequencies, the leads between the coil systems and the switching mechanism must be short and the transmitter made quite compact. This brings the coil systems quite close together. Only one of these coil systems is used at onetime, the others being disconnected from the circuit. At certain frequencies of operation corresponding to the natural period of the unused coils considerable energy may be transferred from the active part of the circuit to the unused coils causing interference-with the operation of the circuit and reduction in efliciency of operation. Voltages in the unused coils may become so high as to cause partial discharge from the ends of the coils. The difficulty is due to both the magnetic and-electric coupling between the active coil and inactive coils. In thesystem of my invention I provide a movable electrostatically shielded inductance'system wherein a multi-' plicity of inductance units of diiIerent frequency I characteristics are disposed in adjacent metallic compartments which operate to magnetically and electrostatically isolate unused inductance units from the selected inductance unit as each selective operation is performed for preventing undesired losses in the transmission system. I provide a frame structure in which there is mounted a pair of rotatably driven shafts. These shafts are simultaneously driven through a gear and crank connection. The shafts are-threaded throughout part of their length and are unthreaded throughout the remainder of their length. Grooves are provided at spaced intervals in the shafts. There are means connected with the compartments for engaging the screw threads on the shafts to enable the compartments to be driven longitudinally of the shafts. There are means connected with the compartments engageable with the grooves in the shafts for providing automatic stops for the compartments at selected positions as the compartments are shifted along the shafts. Inductance units of different frequency characteristics are mounted within the compartments. Taps project through an open side wall of the compartments from each of the inductance units. There is an insulated panel mounted midway of the shafts, which panel carries contact elements extending in the path of the taps on theinductance units. Extending in opposite directions from the insulated panel and immediately adjacent the open side wall of the compartments, I provide shield plates. These shield plates are so shaped and coordinated with the end walls of the compartments that the compartments containing the unused inductance units are effec- 5 tively electrostatically and magnetically shielded. Electrical connection is established between the compartments and the shield plates by means of brushes which project from the shield plates and bear upon the compartments. 40. My invention will be more fully understood -by' a detailed reference to the drawings. The coils 1 are shown mounted in compartments 2 made of suitable metal. These compartments 2 are disposed one on top of the other, the whole forming a rectangularly shaped container which -iscausedtomoveupanddownbytheuseof members 3 and 3'. These members 3-and 3 pass through supports 4, 4', 5 and 5'. Below'points 6 and 6' members 3 and 3' are threaded and engage with threads in 5 and 5'. Above the points 6 and 6' members 3 and 3' are smooth and are free to rotate and slide over members 4 and 4' except forannular grooves 7 and 7' which are provided, in order that the coils maybe located in their proper positions. The upward and downward motion of 2 iscontrolled by means of control 8 by means of which shaft 9 may be'rotated. This causes the rotation of bevel gears 10. 10', 11 and 11' in turn causing rotation of members 3 m and 3'. The gears are supported in bearing members 12 and 12' which are in turn supported from the front and rear panels 13 and 13' by the use of memberl! and angle members 15 and 15'.

Members 3 and 3" are supported at their upper 6 end by bearing-member 16 which isin turn sup ported from the panels 13 and 13' by the use of angle members 17 and 1'1.- The coil compartments 2 areiformed by long vertical membersextending from the bottom to the top of the coil unit. Individual comts are formed. by

the use of horizontal members la'supported'bymembers 19 which make the.

the use of angle whole unit rigid. -Twostationa ryshields 20 andmfprepmvided to shield the open side of compartments 2 together with coil contacts 21. Thelower andupper ends of the end compartments 2 are provided with extension shield members 22 which close 011 the open ends of members 20 and 20. Shields 22 are fastened to the ends of end compartments 2 by use of screws 23 and spacers 24. The coil units move from the extreme lower po-- sition shown to the extreme upper position.

Shields 20 and 20' are supported from sides 13 and 13 by use of angle members 25. The coils l have different frequency characteristics. They are supported in compartments 2 by the use of insulating members 26 and 27 by means of screws 28. In order to assure complete shielding con- .tact,'members 29 are provided which electrically connect shields 20 and 20' to compartments 2. The connection is made at a point adjacent to the coils in use. The sides of compartments 2 adjacent to 20 are opened except for a short portion 30 and 30' which forms a contacting surface for brushes 29. Members 20 and 20 cover the open side of all of the unused coils,

the only partially exposed coil being the one which is connected in the circuit. The taps 21 of this coil engage with connection clips 31 mounted on insulating members 32 projecting between shields 20 and 20. As many contacts as are desired may be used. The connections to external circuits are made by the use of binding posts 33. A very small clearance space 34 to 34' is provided between shields 20, '29 and compartments 2. Clearance is Just sum'cient to prevent excessive friction and also tc prevent leakage of electric or magnetic lines of force. In order to permit taps 21 to pass through the top of shield 20 in the bottom .of shield 20, narrow slots 35 are provided in the extension shield members 22. These slots are just large enough to permit passage of, the contacts but are small enough to prevent leakage of electric and magnetic lines -of force. The position of the coil system is indicated by an indicator 36 which is fastened to 4 as shown at 37 in Fig. 3. Indicator 36 passes through a slot in panel 13 as shown at 38.

Y A locking or stop mechanism is provided as part of 4 and 4 as shown at 39. This is more clearly shown in Fig. 10 in which a pin 40 is caused to engage with grooves 7-7 in members 3 and 3' by means of spring-41. A cap 42 screws on the end of body 43 retaining the spring and pin in place. Members 3 and 3' are free to rotate or slide in mem 4-4 except for the force exerted by pin 40 hich may be overcome by the use of control 8 hen the operator intentionally wishes to ge coil systems. lock mechanism however", prevents vibration from accidental change of the coil systems. It should be noted that in the system illustrated four coils of different frequency characteristics are illustrated. Any number of coils can be used. The number chosen was most suitable for a trans- This mitter having a frequency period of from 4 to 20,000 kilocycles.

The oscillation circuits with which-the frequency changing apparatus of my invention is employed are mounted immediately adjacent the terminal post 33 so that the connection between the oscillation circuits. 'and the selected inductance unit and frequency changer hre maintained extremely short. The unused inductance units are electrostatically and magnetically isolated thereon or therefor.

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same time that an extremely compact structure for the transmitter is afforded.

I have described my invention in one of its preferred embodiments but it will be understood by those skilled in the art that I may depart from the details shown herein and employ modifications of my invention within the scope of the appended claims. The embodiment of my invention shown herein is intended in the illustrative sense and not in the limiting sense.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalty What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. Frequency changing apparatus comprising a frame structure, a pair of longitudinally extending guide members rotatably journaled in said frame structure, screw threads on said guide members extending substantially one-half the length of said'guide members, means for simultaneously driving said'guide members, a set of electrostatically shielded compartments, means for mounting said compartments with respect to said guide members, said means including screw devioes engaging the screw threads on said guide members, inductance units of different frequency characteristics mounted in said compartments, taps extending from said inductance units, a set of fixed contacts disposed in the path of said taps, and electrostatic shields extending in opposite directions with respect to said fixed contacts for effectively shielding each of the unused inductance units from each other in all positions in which said compartments may be shifted in selectively connecting the taps on a particular inductance unit with said fixed contacts.

2. Frequency changing apparatus comprising a frame structure, a pair of shaft members extending through said frame structure, said shaft members being screw threaded throughout a portion of their length, means for rotatably driving said shaft members, a plurality of electrostatically shielded compartments, means connected with said compartments and engaging the screw threads on said rotatable shafts, said compartments being open at one side thereof, inductance units of different frequency characteristics insulatingly supported within said compartments and having taps thereon projecting through the open sides of said compartments, aset of fixed contacts insulatingly supported substantially central of said frame structure and in\ the path of the taps on said inductance units, and shield members extending in opposite direc-'- tions from a position adjacent said fixed contacts for effectively closing the open sides of said compartments as said compartments are shifted to successive positions. for establishing connection between the taps one. selected inductance unit and said fixed contacts.

3. Frequency changing apparatus comprising I a frame structure, a pair of shaft members extending through said frame structure, said shaft members being screw threaded throughout a portion of their length, means for 'rotatably driving said shaft members, a plurality of electrostatically shielded compartments, means connected with said compartments and engaging the screw threads on said rotatable shafts, said compartments being open at one side thereof, inductance units of different frequency characteristics insulatingly supported within said compartments and having taps thereon projecting through the open sides of said compartments, 9. set of fixed contacts insulatingly supported substantially central of said frame structure and in the path of the taps on said inductance units, shield plates disposed in a plane immediately adjacent theopen sides of ,saidcompartments and extending in opposite directions from said fixed contacts, and brush members carried by said shield plates and establishing wiping electrical connection with the walls of said compartments whereby all of the inductance units which are not in use are electrostatically isolated from the selected inductance unit.

4. Frequency changing apparatus comprising a frame structure,a pair of shaft members extending through said frame structure, said shaft members being screw threaded throughout a portion of their length and having grooves disposed at spaced intervals throughout the remainder of. their length, a multiplicity of electrostatically shielded compartments, means connected with said compartments and engaging the screw threads on said shafts, separate means connected with said compartments and engaging said shafts, spring devices carried by said separate means for engaging the grooves in said shafts whereby said compartments may be shifted to selected positions, inductance units of different frequency characteristics disposed in each of said compartments and having taps projecting therefrom through an open side wall of said compartments, an insulated panel mounted centrally of said frame structure, contacts carried by said insulated panel in the path of the taps projecting from said inductance units,-shield plates extending in opposite directions from said insulated panel for substantially closing the open wall of said compartments as said compartments are shifted to selected positions determined by the grooves in said shafts for effecting electrical connection between a selected inductance unit and ed compartments disposed in stacked relation, y

means connected with said compartments and engaging, the screw threads on said shafts, inductance units of different frequency characteristics disposed in said compartments, taps on each of said inductance units projecting through an open side wall of said compartments, an insulated panel mounted centrally of said frame structure, contacts carried by said panel and projecting into the path of said inductance units, electrostatic shield plates extending in opposite directions from said insulated panel immediately adjacent the open side wall of said compartments, said shield plates having side portions coextensive with the end walls of said compartments, brush members carried by the ends of said shield plates adjacent said insulated panel all of the inductance units when an electrical connection is established between the taps on a particular inductance unit and the contacts carried by said panel.

ments, means for producing relative movement between said electrostatically shielded compartments with the inductance units contained therein and said set'o! contacts for selectively connecting any one 01' said inductance units with said set of contacts, and means for electrostatically shielding said set of contacts from the inductance units not connected thereto.

LOUIS A. GEBHARD. 

